Engine Design Research Articles

Numerical model of variable valve timing distribution for a supercharged diesel engine

Recently, there's been a strong drive to improve performance of diesel engines while reducing their greenhouse gases emissions. Techniques like exhaust gas recirculation, turbocharging, and variable valve timing have become widespread. The last technique fine-tunes valve operation based on engine speed, which optimize efficiency and power output while saving fuel. This study zeroes in on a specific 4-cylinder, 4-stroke diesel engine of 1.56-liter, GT-Power software is employed to examine a supercharged version and implementing diverse valve lift techniques. The findings are revealing a substantial 30% increase in power output. At 1000 rpm, power rises from 15.1 kW for the standard engine to 19.72 kW for the modified version. For higher engine speeds, the improvements become even more pronounced, reaching a 66% boost compared to the standard configuration. Furthermore, the newly configured engine showcases an impressive 13% decrease in fuel-specific consumption at elevated engine speeds, contributing to enhanced technical performance and fuel efficiency. The numerical model developed in this study holds the potential to aid in the design of novel diesel engines equipped with variable valve timing systems. To lend further support to these findings, experimental validation is recommended.

Numerical study of film cooling in single-element injector gaseous CH4/O2 rocket engine with coupled wall function

The investigation of film cooling in CH4/O2 rocket engines holds paramount importance in the advancement of rocket propulsion. However, the wall heat flux is always overestimated in numerical simulation processes. Hence, this article proposes a numerical framework that employs the Reynolds averaged Navier–Stokes method to simulate the single-element gaseous CH4/gaseous O2 combustion chamber, which is the basis for rocket engine simulations. The coupled wall function that considers chemical reaction effects is introduced to enhance the accuracy of wall heat flux prediction. The impact of utilizing a coupled wall treatment on the prediction of wall heat flux and its fundamental parameters are examined. In addition, a single-element combustion chamber experiment is performed to validate the simulation. The results demonstrate that the implementation of the coupled wall function hardly influences the main flow characteristics, whereas the wall heat flux calculated with general wall functions shows an overestimation, which can be reduced by the coupled wall function. Finally, the case with a coupled wall function can improve the cooling efficiency with greater accuracy and the cooling systems with optimized design. The proposed numerical framework and the findings of the study provide profound insights that can improve the design and optimization of rocket engines.

Numerical simulation of sound attenuation in an acoustically lined duct in high-temperature air flows

Noise reduction structures are important for the vibration and noise reduction design of aerospace engines. The design of noise-reducing structures often needs to be quickly evaluated via numerical simulations. Hence, the simulation results of the corresponding system are very important for guiding the design of noise-reducing structures. High temperature is one of the key environmental factors that need to be considered when evaluating the sound attenuation process via numerical methods. In this study, numerical simulations of acoustic wave propagation on an acoustic liner structure considering air temperature variations are carried out by using compressible Navier–Stokes equations and the ideal gas equation of state. The results showed that the effect of temperature on sound attenuation under grazing flow conditions is complex. Moreover, an increase in temperature will reduce the transmission loss of the acoustic liner in the grazing flow at high air speed.

Experimental Study of a Homogeneous Charge Compression Ignition Engine Using Hydrogen at High-Altitude Conditions

One of the key factors of the current energy transition is the use of hydrogen (H2) as fuel in energy transformation technologies. This fuel has the advantage of being produced from the most primary forms of energy and has the potential to reduce carbon dioxide (CO2) emissions. In recent years, hydrogen or hydrogen-rich mixtures in internal combustion engines (ICEs) have gained popularity, with numerous reports documenting their use in spark ignition (SI) and compression ignition (CI) engines. Homogeneous charge compression ignition (HCCI) engines have the potential for substantial reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions, and the use of hydrogen along with this kind of combustion could substantially reduce CO2 emissions. However, there have been few reports using hydrogen in HCCI engines, with most studies limited to evaluating technical feasibility, combustion characteristics, engine performance, and emissions in laboratory settings at sea level. This paper presents a study of HCCI combustion using hydrogen in a stationary air-cooled Lombardini 25 LD 425-2 modified diesel engine located at 1495 m above sea level. An experimental phase was conducted to determine the intake temperature requirements and equivalence ratios for stable HCCI combustion. These results were compared with previous research carried out at sea level. To the best knowledge of the authors, this is the first report on the combustion and operational limits for an HCCI engine fueled with hydrogen under the mentioned specific conditions. Equivalence ratios between 0.21 and 0.28 and intake temperatures between 188 °C and 235 °C effectively achieved the HCCI combustion. These temperature values were, on average, 100 °C higher than those reported in previous studies. The maximum value for the indicated mean effective pressure (IMEPn) was 1.75 bar, and the maximum thermal efficiency (ITEn) was 34.5%. The achieved results are important for the design and implementation of HCCI engines running solely on hydrogen in developing countries located at high altitudes above sea level.

Study of on-board equipment of modern uavs

This paper analyzes the development and production of modern unmanned aerial vehicles (UAVs). It is noted that they have the following main systems: glider; propulsion system; power supply system; management system; navigation system; telemetry system; radio communication system. All UAV systems are interconnected and work as one complex mechanism. Depending on the list of combat tasks to be solved, the following devices can be additionally installed on board the UAV: optical-electronic, thermal imaging, radar, radiotechnical, radiation, chemical, bacteriological and other types of reconnaissance systems with small intelligence storage systems; means of setting active radio-electronic jammers; means of aiming and adjusting guided weapons; various means of defeat; means of control and communication with the ground control point; responsible for the state identification system; autonomous flight and automatic landing devices. The work reveals the features of the UAV engine design, it is noted that 4, 6 or more engines are installed on modern helicopter-type UAVs, so-called "multicopters", "quadracopters", "drones". In this work, it is noted that the UAV navigation equipment can have various level of complexity and use several signals coming from sensors of different physical origins to calculate its location. The features of the UAV radio communication system are revealed, which is a set of various lines through which intelligence information of various levels of importance and protection is transmitted. All communication links can use different frequency bands and different relay modes, use different signal-code designs, specially adapted to the importance of the intelligence information being transmitted. It was noted that in the absence of a control command, the UAV goes into autonomous flight mode.

Research on Intelligent Design of Geometric Factor Encoding for Aircraft Engine Turbine Structures

In recent years, with the rapid development of computer technology and artificial intelligence design technology, multiple possible design solutions can be quickly generated by transforming the experience and knowledge of structural design into computer executable rules and algorithms. To achieve intelligent design of aircraft engines, this paper proposes an encoding model for the turbine rotor structure of aircraft engines using geometric encoding technology. The turbine rotor structure of aircraft engines is divided into several units according to geometric similarity types, these units continue to be divided into attribute sets according to their functional types, connection relationships, and material properties. These attribute sets can be encoded using geometric encoding technology. The experiment simulated that these codes, for the point cloud modeling of turbine rotor structure, can be quickly achieved and they combine various algorithms to display the point cloud model of the turbine rotor in the Microsoft Visual studio MFC class library. The results show that by creating geometric codes for the turbine rotor of aircraft engines, it is possible to quickly create and display point cloud models of the turbine rotor structure, laying the foundation for subsequent application of machine learning to solve and find the optimal design solution.

Design of an Efficient Turbofan Engine with Afterburners

In this paper we examine ways to potentially improve the overall efficiency of a turbofan engine with afterburners. A design similar to a turbofan engine used mostly in today’s general commercial aviation aircraft was considered and a study was performed on its components individually using GasTurb and MATLAB software packages. The study revealed that the pressure and the temperature are the two main parameters which affect the overall efficiency of the turbofan engine with afterburners. In addition, the study showed the validation of the analytical results numerically using MATLAB and then visually using GasTurb. Finally, GasTurb was also used to perform the analysis of the 3-D plots that allowed for a complete understanding of how the efficiency of the turbofan engine was affected. As a result, different performance values were found, and showed that a turbofan engine with an afterburner can be made more efficient by increasing the pressure and the temperature in the combustion chambers. Keywords: efficiency, turbofan, afterburners, GasTurb, MATLAB

Computational Evaluation of Turbo- and Electric-Powered Simulators for Turbofan Wind Tunnel Test

Experimental testing of aircraft configurations requires the use of representative engine units to simulate powered-on conditions. For ultra-high-bypass-ratio engines featuring tighter aircraft integration, the installation effects need to be carefully assessed. This paper presents a computational evaluation of two powered simulator models for wind tunnel tests of an ultra-high-bypass-ratio turbofan, based on a traditional air-driven turbo-powered simulator (TPS) and an electric-powered simulator (EPS). Starting from two-dimensional axisymmetric analyses, the design of the baseline turbofan engine and the choice of the duplication parameters of the simulators are described. Several aspects related to the nonreproducibility of the core flow at wind tunnel level are discussed, in terms of mass flow matching, TPS core nozzle pressure ratio, and plug shape of the EPS. The EPS can provide a more faithful reproduction of the flowfield under installation, with an estimated installation drag from 4 to 2 drag counts lower than the reference geometry, compared to the 6 drag counts higher prediction of the TPS.

A DCM-Based Non-Isolated Step-Down DC Transformer

DC transformers have emerged as essential devices for medium voltage DC (MVDC)-low voltage DC (LVDC) distribution systems. However, conventional step-down single-level converters have limits on the voltage level of the MVDC-LVDC distribution system. This paper proposes a non-isolated step-down (NISD) DC transformer based on discontinuous conduction mode (DCM). The proposed structure can withstand high voltage levels by sharing voltages between energy storage modules dividing voltage levels. The proposed NISD DC transformer determines operational modes based on energy storage modules and performs the voltage conversion process. The effectiveness of the proposed NISD DC transformer is verified based on a case study using a power system computer-aided design and electromagnetic transient simulation engine including DC (PSCAD/EMTDC™).

Control Co-Design Optimization of Spacecraft Trajectory and System for Interplanetary Missions

This paper develops a control co-design (CCD) framework to simultaneously optimize the spacecraft’s trajectory and onboard system (rocket engine) and quantify its benefit. An open-loop optimal control problem (two-finite burn Mars missions) is used as the benchmark, and the engine design considers the combustion equilibrium and nozzle geometry. The objective function is the fuel burn. The design variables are the trajectory control parameters (such as burn times, burn directions, and time of flight), initial fuel mass, and engine design parameters (such as throat area, mixture ratio, and chamber pressure). The constraints include the final velocities and positions of spacecraft. Single-point optimizations are conducted for three departure dates in May, July, and September 2020. A multipoint optimization is also performed to balance the engine performance for these dates with 49 design variables and 20 constraints. It is found that the CCD optimizations exhibit 22–28% more fuel burn reduction than the trajectory-only optimization with fixed engine parameters and 16–20% more fuel burn reduction than the decoupled trajectory-engine optimization. The proposed CCD optimization framework can be extended to more spacecraft trajectory control parameters and onboard systems and has the potential to design more efficient spacecraft missions.

Piston geometry and stroke optimization for high efficiency propane spark ignition engines

Propane has unique properties and offers interesting characteristics for high-efficiency spark ignition engines. Its high volatility reduces or completely eliminates fuel-wall wetting and facilitates fuel air mixing. Furthermore, propane has a research octane number of 112 and a high octane sensitivity of 15. Finally, its laminar flame speed is on the same order as that of conventional gasoline, and it exhibits high dilution tolerance. Modern spark ignition internal combustion engines rely on fast combustion rates and high dilution to achieve high brake thermal efficiencies. To accomplish this, high stroke-to-bore ratios and high geometric compression ratios have been used in new engine designs. Therefore, propane’s relatively high laminar flame speeds, high knock resistance, and dilution tolerance make it an excellent candidate fuel for modern spark ignition engines. The objective of this work is to co-optimize the piston geometry and the engine stroke to maximize the efficiency of a spark-ignition engine fueled with propane. 3D computational fluid dynamics (CFD) simulations employing the extended coherent flamelet model were used to study the parametric effects of piston shape and stroke length. A piston geometry based on high performing pistons was parameterized using four controlling parameters. The piston geometry and engine stroke design space was explored using deterministic and quasi-random sampling techniques. A Gaussian process regression model was built using the simulation data to explain the results observed.

Cutting-edge research in physics engines: Exploring parallel technologies, algorithm insights, and upcoming trends

Physics engines, a quintessential product of computer science, have become indispensable tools in simulating physical phenomena through mathematical computations. Their prominence in game development, engineering simulations, and various physics applications is unquestionable. Ensuring their optimization is pivotal for meeting the rigorous demands of practical experiments. The significance of this study is twofold: theoretical foundations and practical necessities. From a theoretical standpoint, this paper delves into the core principles and architectural underpinnings of physics engines. We venture into the integration of multithreading and the application of niche algorithms within these engines. Further analysis illuminates how leveraging these technologies can drastically enhance the performance of a physics engine. In culmination, we propose a robust, feasible theoretical framework for physics engines, filling in the pivotal details. This exploration aims to galvanize and steer the evolution of physics engine design. Addressing practical necessities, our research emphasizes real-world applications of various physics engines. We examine tailored optimization strategies suited for specific needs and investigate methodologies to elevate the operational efficiency of specialized physics engines. This dimension of our study holds substantial real-world implications.

The Growth Engine Concept and Its Potential for an Electrified Aviation Future

Abstract The emerging need for cost- and energy-efficient propulsion systems have shifted the research interest to radical concepts, with several challenges to overcome in order to enter into service. However, revitalizing old yet provably successful engine designs—a practice followed by engine manufacturers over the years—can provide low-risk alternative solutions to move immediate market demands. The paper reviews this approach, known as concept of growth engines or core commonality, and investigates how a geometrically fixed or geometrically similar engine core can be utilized across a family of engines. The development programs of the highly successful CFM56 and PT6 engine families are analyzed, proving the success of this concept over the years. The idea is based on the engineering paradigm of product families and is briefly presented from a theoretical perspective. Implementation methods and simulation tools to initiate, conceptualize, design, and evaluate an engine family program are reviewed. The potential application of engine core commonality into electrified propulsion systems is investigated. Design challenges and opportunities that electrification imposes to the growth engine concept are discussed. Finally, the concept of growth electrified propulsion systems is introduced, conveying future research directions to achieve a successful family of engines for electrified applications.

Thrust-matching and optimization design of turbine-based combined cycle engine with trajectory optimization

Abstract Based on the trajectory optimization method of the Gauss pseudospectral, an aircraft/engine matching method is established for the turbine-based combined cycle (TBCC) engine. For a horizontal-takeoff hypersonic aircraft designed at Mach 5, a thrust-matching analysis of the TBCC engine is performed, and a rocket is integrated for further optimization design. The results show that the aircraft for boost missions should adopt the TBCC thrust with a takeoff thrust-to-weight ratio of 99.8 % to reduce the acceleration time and fuel consumption. In contrast, due to the low thrust-to-weight ratio of the TBCC engine, a high-thrust TBCC increases the inert weight in the cruise phase. Therefore, the aircraft designed for cruise missions should adopt the takeoff thrust-to-weight ratio of 92.0 %. Introducing a rocket whose maximum thrust is 10 % of the takeoff weight could assist the aircraft in overcoming the problem of the “thrust pinch” during the transonic and mode transition. With the assistance of rockets, the optimal takeoff thrust-to-weight ratio is 65.3 % for cruise aircraft, and the cruise range is increased by 18 %. While for the boost aircraft, adopting an optimal TBCC of 86.8 % takeoff thrust-to-weight ratio, the introduced rocket could reduce the fuel consumption and the TBCC engine weight by 4 %.

Integrated Design of a Variable Cycle Engine and Aircraft Thermal Management System

Abstract The integrated design of a variable cycle engine (VCE) and an aircraft thermal management system (TMS) is investigated. The integrated system is designed using the multiple design point approach in order to achieve required performance metrics at points other than the cycle design condition. The VCE architecture is a three stream design where the third stream is split off after the fan, exhausting through a separate third-stream nozzle. The primary air stream passes through a low-pressure compressor before splitting into an inner bypass stream and a core stream. The inner streams mix aft of the low-pressure turbine and exhaust through a core nozzle. The variable cycle engine utilizes variable compressor inlet guide vanes, a variable area bypass injector at the core stream mixing plane, and variable throats in the two exhaust nozzles. The TMS architecture is an air cycle system using air bled from the high-pressure compressor. The effect of integrating the TMS into the engine design loop is investigated. A comparison is made to prior studies where the same TMS architecture was connected to a low bypass ratio turbofan engine. The comparison shows that the variable cycle engine is able to improve heat dissipation capability versus a ram air cooled system, while eliminating the airframe integration impact that comes with a separate ram-air stream. Lastly, the impact of modulating the variable geometry features on overall cooling capability is investigated. Results are presented for individual operating points as well as at the aircraft mission level.

1D simulation analysis and optimization design of engine cooling system

The engine cooling system takes away the heat absorbed by high-temperature parts during the operation of the car engine in a timely manner, keeping it working within the normal temperature range. This article applies Flowmaster software to establish a one-dimensional cooling system model for a certain model of National Five diesel engine. Relevant boundary conditions are inputted to complete steady-state simulation calculations of the system under different operating conditions, obtaining the flow rate, pressure distribution, and temperature rise of each component. At the same time, three optimization schemes are designed based on the original cooling system to predict and evaluate the working capacity of the cooling system, Based on the calculation and analysis results, improvement suggestions are proposed to guide the structural design and testing of the cooling system, greatly reducing research and development time and reducing research and development costs. The calculation results show that the flow rate of each component in the rated point, heating test condition, and idle condition of the original plan has decreased compared to the flow rate of a certain four machine on the same platform under the same working condition (the air compressor flow rate is higher than the limit value), and the temperature difference of the radiator and heating flow rate do not meet the specification requirements. Suggest using Plan 3 to increase the water pump speed ratio to 1.25, with a warm air flow rate of 5.33L/min under idle conditions, which is 72% higher than the original plan and meets the vehicle limit requirements. In addition, to ensure the accuracy and reliability of the model and calculations, this project conducted cooling system tests on an engine bench. The comparison between the simulation calculation data and the experimental data showed that the simulation calculation results were consistent with the experimental results.

Experimental study of spatial distribution of knock events in a turbocharged spark-ignition engine

An experimental investigation on the spatial distribution of knock events in a turbocharged spark-ignition engine for hybrid vehicle applications was conducted by using a multichannel fiber optic method. The knock positions were detected under different conditions to investigate the influence of crucial engine design and operating parameters on the knock characteristics including the spatial distribution in the combustion chamber and its relationship to knock intensity. The measured data reveal that the spatial distribution in the engine with a port fuel injection (PFI) system is mainly located on the exhaust side with insignificant influence of engine speed and load, which is attributed to the elevated thermal load around the exhaust valves. However, the knock events under gasoline direct-injection (DI) conditions were found to occur in more scattered locations with more occurring on the engine front-end and rear-end sides. These results indicate that the in-cylinder fuel-air mixing process may have a significant impact on the knock occurrence spots under DI conditions. The knock positions of the engine with different excessive air ratios, injection timings, and intake-valve timings were also detected, indicating that engine operating parameters have complex influences on the knock-region distribution in a DI engine. In addition, experiments were also carried out in two different cylinders to verify the cylinder-to-cylinder variations in knock regions which may be caused by the engine cooling design. Furthermore, no apparent correlations were observed between the knock position and the knock intensity by analysis of the experimental data.

Managing Technical Staff in a Modern Organization for Successful Business

An obstacle to the introduction of advanced technologies is the shortage of technology specialists. At this time, it is possible to slow down the economic growth of enterprises, as well as to reduce the competitiveness of companies. The reasons for the shortage of qualified personnel are: 1. High rate of introduction of advanced information technologies 2. Rapid growth of e-business 3. Lack of training programs The issue of increasing the effectiveness of personnel management in order to rationally use existing labor resources is very relevant. By stopping the hiring of new employees, managers try to retain technical staff. Issues of labor resource management are still insufficiently studied despite the existence of a serious theoretical and experimental basis. One of the objective reasons that hinders the development of research in this field is the lack of appropriate tools. Modern information technology is the basis that allows a person to expand the researcher's abilities when analyzing the problem under consideration. Managers' requirements for technical staff are determined by: a. Knowledge and experience of working in the existing specialty b. Knowledge of the sales market c. Clarification in the production technologies of a foreign country d. Using them at work There are many categories and within each category there are many different areas, both technical and creative. Engineering and technical personnel can be trained in various directions, such as mechanical engineering, metallurgy, chemical technology, biotechnology, automation, construction, architecture, electrical and radio engineering, food technology, consumer goods research, mechanical engineering, metallurgy, automation, energy, assistance in the adoption of transport process technologies, Thermal energy and heating engineering, personnel training for radio-electronic systems, aircraft engine designers, future fashion designers and other fields. Today young people believe that technical professions are not as prestigious as, for example, a web designer or a photographer. Keywords: technical staff, personnel management, successful business, modern organization.

Optimizing design of a free piston Stirling engine using response surface methodology and grey relation analysis

The performance analysis and optimization of a γ-type free-piston Stirling engine (FPSE) are conducted using Response Surface Methodology (RSM) and Grey Relation Analysis (GRA). The input-output parameters table is determined by the RSM. A regression model is presented to investigate the influence of structural parameters of FPSE on its performance. The relation coefficients for the four output parameters obtained from the RSM are determined to be 0.9980, 0.9983, 0.9999, and 0.9995, respectively, thus unequivocally demonstrating the exceptional precision of the RSM model. Also, the relationship between displacer and piston amplitudes, operating frequency, and output power and these parameters of Stirling engine is presented via 3D surface plots. The performance of the FPSE is optimized using the desirability approach and GRA, respectively, followed by a comparison of four groups of optimization results to determine the most suitable model. The maximum output power achieved is 78.02 W, with corresponding operating frequency, displacer amplitude, and piston amplitude values of 60.24 Hz, 2.55 mm, and 7.27 mm. Finally, by comparing pre- and post-optimization, the output power is increased by 36.85%. The GRA exhibits superior optimization compared to the RSM, thus providing valuable guidance for enhancing the optimization of FPSE in this study.

Equivalent simulation method for total pressure distortion of ship inlet

According to the use of marine gas turbines, inlet distortion is caused by the bending of the compressor inlet port. The total pressure distortion is the external stability reduction factor that has the greatest impact on the engine’s aerodynamic stability. This research designs a pressure distortion simulation device, which achieves the goal of providing the target distortion flow field for marine compressors by inserting plugboards of different heights and shapes into the inlet duct. The variation pattern of the entire flow field after inserting different parameter plugboards is obtained through distortion experiments and numerical simulations. Summarizes a prediction formula for total pressure distortion under different working conditions, with a verified error of less than 1.5%. In addition, the straight plugboard is changed to arc plugboard or concave and convex plugboard, the total pressure distortion distribution pattern can be changed while the range of the circumferential low-pressure zone remains unchanged. The distortion index of the distortion simulator designed by this research institute can be adjusted within the range of 0.5%–5%, while providing various distortion pattern. The distortion simulator meets the requirements of the comprehensive distortion index needed for the relevant distortion test of the marine engine and provides assistance for ship engine design and optimization.